1. Field of the Invention
This invention relates to a toner used in recording processes utilizing electrophotography or electrostatic recording. More particularly, this invention relates to a toner used in copying machines, printers or facsimile machines in which an electrostatic latent image formed on an electrostatic latent image bearing member is developed with a toner to form a toner image on the electrostatic latent image bearing member, the toner image on the electrostatic latent image bearing member is transferred to a transfer material via, or no via, an intermediate transfer member, and the toner image on the transfer material is fixed thereto to form a fixed image.
2. Related Background Art
The electrophotography is a process in which an electrostatic latent image bearing member formed of a photoconductive substance is electrostatically charged by various means and is further exposed to light to form an electrostatic latent image on the surface of the electrostatic latent image bearing member, the electrostatic latent image is then developed with a toner to form a toner image, the toner image is transferred to a transfer material such as paper, and the toner image transferred to the transfer material is fixed to the transfer material by the action of heat or pressure or heat and pressure to obtain a copy or a print.
However, when such an image formation process is repeated in a large number especially in a high-humidity environment, ozone produced in the step of charging where the electrostatic latent image bearing member is electrostatically charged may react with oxygen in air to turn into nitrogen oxides (NOx), and these nitrogen oxides may further react with water in air to turn into nitric acid to come to adhere to the surface of the electrostatic latent image bearing member, resulting in a lowering of surface resistance of the electrostatic latent image bearing member. This may cause smeared images on the electrostatic latent image bearing member at the time of image formation. As measures against such smeared images, a method is known in which particles having abrasive action are added to toner base particles to strip charge products having adhered to the surface of the electrostatic latent image bearing member to make an improvement. However, such an abrasive agent has a large particle diameter and a broad particle size distribution, and hence it has been difficult to uniformly abrade the surface of the electrostatic latent image bearing member.
As methods having made an improvement in this regard, methods are proposed as disclosed in Japanese Patent Application Laid-Open No. H10-10770 and Japanese Patent No. 3047900 in which strontium titanate powder is added to toner base particles. The strontium titanate powder used in these methods has fine particle diameter and contain only a few coarse particles, and hence has good abrasive effect. The strontium titanate powder used in these methods is effective for preventing filming or melt adhesion from being caused by the toner to the electrostatic latent image bearing member. However, this powder has been insufficient for removing the above charge products.
As disclosed in Japanese Patent Application Laid-Open No. 2000-162812, a method is proposed in which toner base particles containing an abrasive substance and a fatty acid metal salt are used; in Japanese Patent Application Laid-Open No. H08-272132, a method in which a fatty acid metal salt and a titanic acid compound are externally added to toner base particles; and in Japanese Patent Application Laid-Open No. 2001-296688, a method in which a metal oxide surface-treated with a lubricant such as a fatty acid metal salt is externally added to toner base particles. However, these methods have all been insufficient for removing the charge products.